By default, the mod provides descriptions for all Vanilla Minecraft entities as well, and uses a similar format to blocks. To add a tooltip to an entity, just add the following entry to your mod or resource pack's language file (en_us.json for English U.S.).
"entity.<namespace>.<your_entity_here>.description": "A mysterious modded entity."For example, if I wanted to add a description to Chaos Pawns from Infinite Dimensions, I would add the following entry to Infinite Dimensions's language file.
"entity.infinity.chaos_pawn.description": "This neutral mob spawns in Infinity Portals. It will randomly drop any item when killed."When adding new tooltips, its recommended to keep them two sentences or less to match the ones present in the original mod.